How to get the clients host name behind apache2 reverse proxy and tomcat server?

Question

I'm using apache2 as a reverse proxy in front of a tomcat8 server. I already make use of X-Forwarded-For to find the clients IP address.

But my goal is to get the clients hostname . Is that possible at all? Would I have to tell this to apache or to tomcat?

Answer 1

Through http, you'll get the client's public IP address, which might be their proxy, or their NAT router. You can use that IP address for a reverse DNS lookup, but as client computers rarely have publicly addressable DNS entries, you'll not get far. (In fact, you've asked precisely that question as well and got a good answer there)

As this question is specifically about the hostname , not about the DNS entry, here's where this answer differs from the answer to your other question:

The only option that I see to get to the hostname itself (something like "John's Mac") would be if the browser reveals it - eg through Javascript. If a browser would allow that, I'm sure that all the ad networks would be salivating over this leak of information. That's the reason why I expect the actual hostname being unavailable to you, without even looking up any option.